This is a summary of the U.S. Geological Survey (USGS) National Water-Quality Assessment (NAWQA) Program study of water quality in carbonate aquifers of the United States. More than 1,000 wells and springs were analyzed for properties and contaminants including pH, major ions, nutrients, trace elements, radon, pesticides, and volatile organic compounds, in 12 carbonate aquifers in the United States.

Carbonate aquifers are the most widely used of all bedrock aquifers, and provide 22 percent of the United States public ground-water supply. Carbonate aquifers are those aquifers in limestone or dolomite bedrock. The NAWQA program has sampled well networks in many carbonate aquifers using similar methodologies, and thus provided one of the first opportunities to evaluate water quality in the various carbonate aquifers. This web site is a supplement to the National Water-Quality Assessment Program's report: Factors affecting water quality in selected carbonate aquifers in the United States, 1993-2005: Scientific Investigations Report 2008-5240. The site highlights the findings of this report, and provides additional details about the study.